This invention relates to the repair of overhead valve mechanisms for internal combustion engines. For many years it has been known that certain valve train repairs can be accomplished without removing the cylinder head or heads. Typically, broken or weak valve springs, or related parts, can be removed and replaced by removing the valve cover and whatever of the rocker arms as are necessary. Such repair operations are possible on both push-rod and overhead cam assemblies.
With the more recent use of high speed, high compression engines, and with metalurgical and other quality improvements in overhead valve components, the parts that require interim repair or replacement are the valve stem seals or shields. These are intended to inhibit flow of lubricant along the valve stem, through the valve guides and into the cylinders. Wear or failure of these seals or shields can result in excessive lubricant consumption and/or fouling of the corresponding spark plugs or cylinders.
Often, engines can be repaired for many additional miles (or hours) of efficient satisfactory service, merely by replacing the valve stem seals at relatively little expense.
U.S. Pat. No. 1,898,720 of Feb. 21, 1933 illustrates and describes devices for admitting air into cylinders from which valve spring tension has been released. Typically this procedure has been accomplished one cylinder at a time.